1. Field of the Invention
The invention relates to apparatus for a raster image processor, that is capable of driving a printing engine at a high rate, for use in illustratively an image management system.
2. Description of the Prior Art
For various reasons, storage of documents is becoming an increasingly pressing problem for most businesses today. As set forth below, computerized information retrieval systems provide an efficient solution.
Generally speaking and by way of background, there are several steps and many documents involved in a typical business transaction. In particular, paper documents (such as, for example, purchase orders and outgoing bills) are first obtained from several sources. Next, information from these documents is typically entered, through one or more computer terminals, into various computer databases that form part of a computerized filing system. Thereafter, the paper documents are sorted and stored in a paper file for subsequent use. Since valuable information can be quickly accessed from these databases, use of such a computer filing system makes document handling quite efficient. However, when users cannot obtain all the information they need from the databases, they are forced to access the actual documents that have been stored in the paper file. The paper file for a given transaction usually contains a variety of documents: the original document for that transaction (e.g. a specific purchase order for certain goods), associated reference documents that show the history of the transaction (e.g. quotations, manufacturing papers and bills of lading respectively showing that the exact nature of the goods quoted, that these goods have been manufactured and thereafter shipped to the customer) and annotations (notes) relating to the transaction (such as past actions and/or future plans) that exist either on separate documents or appear on the original document itself. As a result, the paper file for any one transaction is often quite voluminous.
Unfortunately, many problems arise when documents are stored in paper form. First, as the number of documents increases, the cost of storing all the documents and accessing any one document correspondingly increases, often substantially. This cost typically includes: the cost of labor needed to maintain the paper files; the cost of delivering the documents in paper form, which typically includes the cost of maintaining and operating copying equipment and microfilm readers and copiers; the cost of physical storage devices, such as cabinets; and, lastly, the cost of the space required to house the documents and all ancillary equipment. Second, paper documents for any transaction are usually filed by only one parameter, typically a name of one of the parties involved in that transaction. As a result, gaining access to a specific document can be extraordinarily arduous and time consuming, if this document is to be accessed by a parameter other than that under which it has been filed. Third, to reduce storage costs, paper files usually contain only one copy of a document, typically the original itself. As a result, only one user can examine a paper document at a time. Hence, if several users desire simultaneous access to a document, only one user can be serviced at any given time and all the other users must wait their respective turns to obtain access. This wastes time and effort. Fourth, paper files are often disorganized, incomplete and frequently lost. Consequently, as the number of paper files grows in size, information often becomes increasingly hard to find and productivity of those that depend upon these files correspondingly decreases.
In recognition of these problems, the art has turned to the use of computer based document storage systems. Early attempts, so-called computer assisted retrieval of microimage (CAR) systems, relied on microfilming the document and recording pertinent identifying information in a computer database. This information included a unique microfilm address (typically microfilm roll and frame numbers) which specified where, on microfilm, the document was stored and data relating to the document itself (parties involved, type of document and the like). This database could be quickly searched using any one of several parameters to readily locate the address of a particular document. With the address in hand, a user could quickly retrieve a particular roll of microfilm and, using a microfilm reader, manually access the desired document that has been stored in the roll. Once this document has been accessed, the microfilm reader prints a paper copy image of the document. Inasmuch as a microfilm copy often legally serves the function of a paper copy, the original document can be destroyed after it has been microfilmed. Such a system advantageously eliminates the need for paper files and the problems associated therewith.
Since the computer in a CAR system only provides microfilm addresses, the image produced by a CAR system is exactly that which was recorded on microfilm. As such, CAR systems do not possess any ability to process and manipulate these images electronically.
Consequently, CAR systems, though providing significant advantages over paper files, contain several drawbacks. First, microfilm images often contain noise. CAR systems can not remove noise from a microfilm image in order to enhance the image quality. In addition, wide documents are often twisted ninety degrees to facilitate filming in a lengthwise fashion. CAR systems can not rotate accessed documents. Furthermore, a user frequently desires to focus (zoom) into a particular area of an image, for example to read fine print. CAR systems can not electronically expand a desired region of an image. Therefore, print that is difficult to read in the original document remains difficult to read when an image of that document is produced by a CAR system. Moreover, the output speed of a CAR system is limited to that of the microfilm readers. Inasmuch as these readers are often manually operated, significant amounts of time are often expended in accessing and printing documents that contain a substantial number of pages.
Consequently, image management systems have been developed in the art in order to overcome the limitations of a CAR system while still retaining the advantages of a microfilm based system. As in a CAR system, an image management system uses a computer to locate a particular microfilm address of a desired image. However, unlike a CAR system, each accessed microfilm image is then scanned, i.e. digitized, rather than merely being printed. Once the image has been scanned, it is then processed electronically in order to overcome the limitations of a CAR system.
Specifically, one such image management system, presently manufactured by the present assignee and referred to as the Kodak Image Management (KIM) system, relies on applying the scanned image onto a local area network. This network provides a communications link between various workstations and various computer peripherals, such as printers and mass storage devices (e.g. disk drives). In this system, an image can be sent to a workstation which appropriately processes the image, as instructed by the user. For example, the user can instruct the workstation to rotate the image and/or zoom into and expand a desired area of the image. Thereafter, the user can instruct the workstation to route the processed image to a printer to form a paper copy of the image and/or route the processed image to memory from which it can be accessed by other workstations for subsequent processing and printing. Such a system readily permits each user to append annotations to an accessed image. An annotation is typically writing, e.g. a comment, that has been overlaid onto a desired area of an image by a user. In particular, a user situated at a KIM workstation first accesses a microfilm image through the workstation, positions a cursor at a desired location on the image and types a comment (an annotation) onto the image. The workstation, in turn, instructs the KIM system to store the comment in memory along with the addresses of both the corresponding accessed image and the desired image location. Subsequently, whenever another user accesses the same microfilm image, that image is digitized and the comment is automatically read from memory. The workstation then overlays the comment onto the image at the proper location and displays the result.
While image management systems, such as KIM systems, overcome the drawbacks associated with CAR systems, image management systems have heretofore not possessed a sufficient throughput to satisfy the needs of large volume users. In particular, image management systems include a raster image processor (RIP) which appropriately processes a scanned microfilm image, in a manner desired by the user, and thereafter routes the processed image either to a printer and/or to a local area network. Currently, high quality image printers, such as various laser printers, that possess the capability to print high quality images at a rate in excess of 10 pages/minute are becoming readily available. However, RIPs known to the art are quite slow and, as such, do not provide processed images as output data at a rate commensurate with the throughput of an image printer. Consequently, processing delays inherent in the RIP substantially limit the throughput of an image management system.
These delays develop primarily because the entire image, often a large bit-map, is sequentially routed through and processed by the central processing unit, typically a microprocessor, situated within the RIP. In use, a RIP first transfers a compressed image from the local area network to a frame store memory. This memory is used to temporarily store the image during subsequent decompression and image processing. Once this transfer is complete, the microprocessor decompresses the image prior to performing image processing. After this processing has been completed, the processed decompressed image is typically transferred from the frame store memory to an image printer for printing. The architecture of RIPs known in the art often mandates that the image must disadvantageously pass through the microprocessor during any such transfer. Unfortunately, excessive processing time is consumed in performing either image decompression or an input/output (I/O) transfer of a large bit-mapped image.
In particular, to maximize the efficiency of the network and mass storage devices used therein, a microfilm image is typically compressed, using single or two dimensional run length coding, prior to being transmitted over the local area network. Once an image is received by a RIP, the RIP decompresses the image prior to displaying and/or subsequently processing the image. Most currently available RIPs are microprocessor based with the decompression process implemented in software. Owing to the complexity of the processing required to decompress even a small area of an image, e.g. a one inch square area, decompressing a complete image may require upwards of fifteen minutes of processing time even using a 32 bit microprocessor operating at high clock rates. As a result, such RIPs operating on compressed bit-mapped image data can not generate output data for printing at a rate that even approaches one page/minute.
Moreover, RIPs known in the art are generally unable to perform simple I/O transfers of bit-mapped image data at a sufficiently rapid rate to match the input rate of an image printer. Typically, a single uncompressed bi-tonal image bit-map, of the type generally applied to an image printer, may contain upwards of 3-4 Mbytes of pixel data. Presently available high speed microprocessors require approximately 3 microseconds to perform an I/O transfer of one pixel of image data from a frame store memory to an image printer. As such, these microprocessors are simply incapable of transferring 10 complete uncompressed images per minute to an image printer.
Inasmuch as these microprocessors are incapable of decompressing, processing and transferring ten complete bit-mapped images per minute between a local area network and an image printer, the throughput of available image management systems has been disadvantageously limited by the use of RIPs known in the art.
Therefore, a need exists in the art for a raster image processor that operates on incoming compressed bit mapped images at a rate commensurate with the throughput of currently available high quality image printers. Such a RIP will advantageously facilitate the implementation of high throughput image management systems.